I reload for my .223 Mini-14s, Contender, and .223-12ga Over and under. I get my best results with W-748. I got good results with IMR-3031 also. I do not reload for my H&R Ultra since it likes Ultramax remanufactured ammo, and they load the bullet I like. 50gr Nosler Ballistic tip.
First you will need a reloading manual, I would recommend the one put out by the bullets you will most likely use, like Nosler. After reading the getting started section you will better understand what you will need. As for trimming the cases, I like Lee case trimmers and I use them with my electric screwdriver. I have one set up for every caliber I reload. If your relative already has an RCBS case trimmer all you will need is the pilot for .223. While sitting watching TV some evening I will go through a bunch of cases trimming them to length, deburring the case mouth with a deburring tool at the same time while I have the case locked in the trimmer base. This also allows me to inspect each case for cracks, deformities, or any other problems I might catch during inspection.
Hogden puts out a good inexpensive manual yearly also. I get my W-748 loads from it as well as the Nosler manual. Nosler list w-748 as the most accurate powder tested.